We investigate the dynamics of heterogeneous beliefs and link them to the volatility pattern throughout the seasoned equity offering (SEO) event window. In sync with a reduction in information asymmetry related to management information releases around the SEO event, belief heterogeneity declines. Moreover, heterogeneity in beliefs, proxied by either analyst- or institutional-trade-based measures, is a robust and salient determinant of SEO firm volatility, which provides an explanation for the volatility timing “puzzle” identified in the SEO market. Furthermore, the relation between heterogeneous beliefs and return volatility weakens as short sale constraints tighten, suggesting a potential causal link.